Question: A group of adults and kids went to see a movie. Tickets cost $$6.00$ each for adults and $$4.50$ each for kids, and the group paid $$30.00$ in total. There were $2$ fewer adults than kids in the group. Find the number of adults and kids in the group.
Explanation: Let $x$ equal the number of adults and $y$ equal the number of kids. The system of equations is then: ${6x+4.5y = 30}$ ${x = y-2}$ Solve for $x$ and $y$ using substitution. Since $x$ has already been solved for, substitute ${y-2}$ for $x$ in the first equation. ${6}{(y-2)}{+ 4.5y = 30}$ Simplify and solve for $y$ $ 6y-12 + 4.5y = 30 $ $ 10.5y-12 = 30 $ $ 10.5y = 42 $ $ y = \dfrac{42}{10.5} $ ${y = 4}$ Now that you know ${y = 4}$ , plug it back into ${x = y-2}$ to find $x$ ${x = }{(4)}{ - 2}$ ${x = 2}$ You can also plug ${y = 4}$ into ${6x+4.5y = 30}$ and get the same answer for $x$ ${6x + 4.5}{(4)}{= 30}$ ${x = 2}$ There were $2$ adults and $4$ kids.